Stem cells refer to cells capable of differentiating into at least two cells while having self-replicating ability and may be classified into totipotent stem cells, pluripotent stem cells, and multipotent stem cells.
Totipotent stem cells are cells having totipotent properties capable of developing into one perfect individual, and these properties are possessed by cells that have up to eight-cell stages after fertilization of an egg and a sperm. When these cells are isolated and transplanted into the uterus, these cells may develop into one complete individual. Pluripotent stem cells, which are cells capable of developing into various cells and tissue derived from the ectodermal, mesodermal and endodermal layers, are derived from an inner cell mass located inside of blastocysts generated after 4-5 days of fertilization. These cells are called “embryonic stem cells” and may differentiate into various other tissue cells, but do not form new living organisms. Multipotent stem cells are stem cells capable of differentiating into only cells specific to tissue and organs containing these cells.
Multipotent stem cells were first isolated from an adult bone marrow (Y. Jiang et al., Nature, 418:41, 2002), and thereafter, they were confirmed in several other adult tissue (C. M. Verfaillie et al., Trends Cell Biol. 12:502, 2002). However, stem cells in adult tissue such as bone marrow are very rarely present, and it is difficult to culture these cells without differentiation induction, and accordingly, it is difficult to culture these cells without specifically screened media. That is, there is disadvantage in that it is very difficult to isolate the stem cells and preserve the cells in vitro.
Recently, it was found that adipose tissue are new sources of multipotent stem cells (B. Cousin et al., BBRC, 301:1016, 2003; A. Miranville et al., Circulation, 110:349, 2004; S. Gronthos et al., J. Cell Physiol. 189:54, 2001; M. J. Seo et al., BBRC, 328:258, 2005), and it was reported that undifferentiated cell populations are included in human adipose tissue obtained by adipose extraction (liposuction), and have differentiation potency into adipose cells, bone forming cells, myoblast, and chondroblast in vitro (P. A. Zuk et al., Tissue Eng. 7:211, 2001; A. M. Rodriguez et al., BBRC, 315:255, 2004). In addition, it has been known through animal model experiments that adipose tissue-derived cells have a muscle regeneration ability and an ability to promote neurovascular differentiation. The adipose tissue has an advantage of being able to be extracted in a large amount, and accordingly, it has received attention as a new source of stem cells complementing the existing disadvantages.
The stem cells capable of being obtained in a large amount have been increasingly used as a cell therapeutic agent for injecting the stem cells themselves for the main purpose of medicine fields including treatment of incurable diseases, etc., and beauty, cosmetic, etc.
The stem cells for the purpose of the cell therapeutic agent have no problem when medical procedure is directly available to patients after culturing the stem cells. However, when it is required to control time for a medical procedure of stem cells depending on a patient's condition, long-term storage is required after culturing the stem cells. In addition, even when long-distance transport up to a place for practicing the cultured stem cells is required, it is essential to stably supply the stem cells. To this end, it is required to maintain a high survival rate of stem cells for a long period of time for about 5 to 10 days. However, currently, when the stem cells are maintained for a long period of time without freezing, there is a problem in that a cell survival rate is remarkably low. Meanwhile, a cell freezing method causes a remarkably deteriorated cell survival rate when thawed, and has problems on functionality, etc., as the stem cells from a biological perspective. In addition, transport in a freezing state is more difficult than transport in a refrigeration state.
As the conventional current technology of preserving the stem cells in the refrigeration state, there is a technology of suspending and storing human adipose tissue-derived mesenchymal stem cells in saline under refrigeration condition, but in this case, it is difficult to have a survival rate of 70% or more when storing the cells for 48 hours or more. It was confirmed that when sucrose or albumin is added to overcome the difficulty, the survival rate is 70% or more up to 48 hours to 72 hours, and storage stability is improved (Korean Patent Laid-Open Publication No. 10-2008-0103637). However, after 72 hours, since the survival rate is rapidly reduced, it is required to develop a composition for improving storage stability under refrigeration condition (4° C.) so that the survival rate of the stem cells included in cell therapeutic agents is stably maintained to be high for a long period of time.
Therefore, the present inventors made an effort to maintain the survival rate of the stem cells to be high even for a long-time cold-storage, and as a result, found that when blood serum or blood plasma is contained, the survival rate of the stem cell in a refrigeration state is maintained to be high for at least 9 days, and completed the present invention. There is a case in which human blood serum is used as a medium composition for cell culture (Korean Patent No. 10-0394430); however, a composition for improving storage stability of stem cells containing human blood serum or human blood plasma has not been disclosed.